Paw Justice began a campaign called Don't Trade Me In 2015, calling for the complete ban of pet sales on the website due to concerns around puppy mills and dog welfare.

At the time, Trade Me began working on a code of responsible breeding for dogs and cats. Since then, a Code of Animal Welfare was introduced, which contains guidelines on puppy socialisation, the age when puppies can be released to their new owner and the mother's health and breeding history.

If a member's listing states it complies with the code, they must also disclose whether the puppy or parents had undergone surgery to correct inheritable problems, if there were any potential breed-specific concerns, and whether the parents were related within two generations.

But more was needed than just "ticking a little box", as the code did not necessarily stop "backyard breeders" or people potentially running puppy mills using the site as a platform to sell commercially-bred dogs, Dunn said.

"It's very self-regulating and it's not satisfactory for us."

However, Dunn said he was supportive of registered charities using the platform for rescue animals.

Trade Me's policy and compliance team leader James Ryan said banning the sale of all dogs would be "using a sledge hammer to crack a nut".

The Code of Animal Welfare was voluntary because it "cannot realistically cover all circumstances" under which the sale of an animal could occur, he said.

The website's trust and safety team monitored the site 24/7 and worked closely with the SPCA, Ryan said.

"If we have concerns about a breeder or an animal we will forward this information onto the SPCA [which] will check it out."

Trade Me was not aware of any members who had falsely stated their animal listing met the Code of Animal Welfare, he said.

Users who were concerned about a seller or a listing were encouraged to alert the Trade Me team via the 'Community Watch' badge.